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The multi-modality cardiac imaging approach to the Athlete's heart: an expert consensus of the European Association of Cardiovascular Imaging. ; ; et al in European heart journal cardiovascular Imaging (2015) The term 'athlete's heart' refers to a clinical picture characterized by a slow heart rate and enlargement of the heart. A multi-modality imaging approach to the athlete's heart aims to differentiate ... [more ▼] The term 'athlete's heart' refers to a clinical picture characterized by a slow heart rate and enlargement of the heart. A multi-modality imaging approach to the athlete's heart aims to differentiate physiological changes due to intensive training in the athlete's heart from serious cardiac diseases with similar morphological features. Imaging assessment of the athlete's heart should begin with a thorough echocardiographic examination. Left ventricular (LV) wall thickness by echocardiography can contribute to the distinction between athlete's LV hypertrophy and hypertrophic cardiomyopathy (HCM). LV end-diastolic diameter becomes larger (>55 mm) than the normal limits only in end-stage HCM patients when the LV ejection fraction is <50%. Patients with HCM also show early impairment of LV diastolic function, whereas athletes have normal diastolic function. When echocardiography cannot provide a clear differential diagnosis, cardiac magnetic resonance (CMR) imaging should be performed. With CMR, accurate morphological and functional assessment can be made. Tissue characterization by late gadolinium enhancement may show a distinctive, non-ischaemic pattern in HCM and a variety of other myocardial conditions such as idiopathic dilated cardiomyopathy or myocarditis. The work-up of athletes with suspected coronary artery disease should start with an exercise ECG. In athletes with inconclusive exercise ECG results, exercise stress echocardiography should be considered. Nuclear cardiology techniques, coronary cardiac tomography (CCT) and/or CMR may be performed in selected cases. Owing to radiation exposure and the young age of most athletes, the use of CCT and nuclear cardiology techniques should be restricted to athletes with unclear stress echocardiography or CMR. [less ▲] Detailed reference viewed: 26 (2 ULg)Multi-Months Cycles Observed in Climatic Data Nicolay, Samuel ; Mabille, Georges ; Fettweis, Xavier et al in Simard, Suzanne (Ed.) Climate Change and Variability (2010) Climatic variations happen at all time scales and since the origins of these variations are usually of very complex nature, climatic signals are indeed chaotic data. The identification of the cycles ... [more ▼] Climatic variations happen at all time scales and since the origins of these variations are usually of very complex nature, climatic signals are indeed chaotic data. The identification of the cycles induced by the natural climatic variability is therefore a knotty problem, yet the knowing of these cycles is crucial to better understand and explain the climate (with interests for weather forecasting and climate change projections). Due to the non-stationary nature of the climatic time series, the simplest Fourier-based methods are inefficient for such applications (see e.g. Titchmarsh (1948)). This maybe explains why so few systematic spectral studies have been performed on the numerous datasets allowing to describe some aspects of the climate variability (e.g. climatic indices, temperature data). However, some recent studies (e.g. Matyasovszky (2009); Paluš & Novotná (2006)) show the existence of multi-year cycles in some specific climatic data. This shows that the emergence of new tools issued from signal analysis allows to extract sharper information from time series. Here, we use a wavelet-based methodology to detect cycles in air-surface temperatures obtained from worldwide weather stations, NCEP/NCAR reanalysis data, climatic indices and some paleoclimatic data. This technique reveals the existence of universal rhythms associated with the periods of 30 and 43 months. However, these cycles do not affect the temperature of the globe uniformly. The regions under the influence of the AO/NAO indices are influenced by a 30 months period cycle, while the areas related to the ENSO index are affected by a 43 months period cycle; as expected, the corresponding indices display the same cycle. We next show that the observed periods are statistically relevant. Finally, we consider some mechanisms that could induce such cycles. This chapter is based on the results obtained in Mabille & Nicolay (2009); Nicolay et al. (2009; 2010). [less ▲] Detailed reference viewed: 89 (19 ULg)Multi-national, Multi-cultural and Multi-levelled Brussels : National and Ethnic Politics in the « Capital of Europe » Martiniello, Marco ; in Fonseca, Maria-Lucinda (Ed.) Cities in Movement : Migrants and Urban Change (2008) Detailed reference viewed: 57 (2 ULg)Multi-national, multi-cultural and multi-levelled Brussels: national and ethnic politics in the "Capital of Europe" Martiniello, Marco ; Book published by The Transnational Communities Programme, University of Oxford (1999) Detailed reference viewed: 29 (2 ULg)Multi-Objective Optimization of a Fan Blade by Coupling a Genetic Algorithm and a Parametric Flow Solver Kelner, Vincent ; ; Léonard, Olivier et al in Proceedings of EUROGEN'05 (2005, September) Detailed reference viewed: 44 (0 ULg)Multi-party Arbitration under the UNCITRAL Rules Kohl, Benoît Conference (2008, May 15) Detailed reference viewed: 80 (9 ULg)Multi-period Stochastic Optimization Problems in Transportation Management Pironet, Thierry Doctoral thesis (2014) The topic of this thesis in management science is to propose a methodology to tackle multi-period decision problems including stochastic forecasts and to apply it to the field of transportation management ... [more ▼] The topic of this thesis in management science is to propose a methodology to tackle multi-period decision problems including stochastic forecasts and to apply it to the field of transportation management. This methodology relies mostly on a sequence of numerical experimentations based on a set of algorithms to assess the value of the multi-period setting and the interest to use the stochastic information contained in the forecasts. Moreover, a statistical validation method to compare the performances of algorithms enables us to rank them meaningfully. From theory to practice, the thesis is structured into four parts. Firstly, we define the thesis subject and content. Then, based on a literature review, we present the past and present issues within the research field: "Optimization in Transportation". Mainly, we define the differences between multi-period stochastic models and classical deterministic mono-period ones. We explain how dynamism and stochasticity are taken into account within transportation problems. Secondly, our methodology, which is our main contribution, is exposed from a generic point of view in the theoretical research field: "Multi-period Stochastic Optimization Problems". On the one hand, temporal parameters and computational issues in multi-period optimization are detailed; on the other hand a summary of optimization techniques and algorithms for stochastic optimization problems is provided. Afterwards, the statistical validation of algorithmic performance is discussed. Then, part three contains two applications that lead us to set up the methodology, following an inductive method. The first problem, based on an industrial application at the start of the research, investigates a "multi-period vehicle loading problem with stochastic release dates". The second application, based on a more generic approach for the deployment of the methodology, deals with a "multi-period vehicle assignment problem with stochastic load availability". Finally, in the fourth part, we conclude on the thesis contributions and propose some perspectives. [less ▲] Detailed reference viewed: 152 (14 ULg)Multi-period stochastic optimization problems in transportation management (Ph. D. Thesis Summary) Pironet, Thierry in 4OR : Quarterly Journal of the Belgian, French and Italian Operations Research Societies (2015), 13(1), 113-114 Ph. D Thesis summary see other reference on ORBI Detailed reference viewed: 27 (4 ULg)Multi-period vehicle allocation with uncertain transportation requests Crama, Yves ; Pironet, Thierry E-print/Working paper (2015) This work investigates optimization techniques for a multi-period vehicle allocation problem with uncertain requests. A company owning a limited fleet of trucks attempts to maximize its operational profit ... [more ▼] This work investigates optimization techniques for a multi-period vehicle allocation problem with uncertain requests. A company owning a limited fleet of trucks attempts to maximize its operational profit over an infinite horizon by optimally assigning transportation orders to the vehicles. Its profit stems from profits collected when transporting full truckloads, minus costs incurred when waiting or when moving unladen. The stochastic component of the problem arises from the uncertainty on the realization of each transportation order. The methodology is based on optimizing decisions for deterministic scenarios. Several policies are generated in this way, either by simple heuristics, or by more complex approaches, such as consensus and restricted expectation algorithms, or from network flow formulations over subtrees of scenarios. Myopic and a-posteriori deterministic optimization models are used to compute bounds allowing for performance evaluation. Numerical experiments are performed on various instances featuring different numbers of orders, graph sizes, sparsity, and probability distributions, and the performance of the algorithms is assessed by statistical tests. The robustness of various policies with respect to erroneous evaluations of the probability distributions is also analyzed. [less ▲] Detailed reference viewed: 131 (15 ULg)Multi-period vehicle assignment problem with stochastic transportation order availability Pironet, Thierry ; Crama, Yves Conference (2015, June 01) This work investigates optimization techniques for a vehicle-load assignment problem. A company owning a limited fleet of vehicles wants to maximize its operational profit over an infinite horizon divided ... [more ▼] This work investigates optimization techniques for a vehicle-load assignment problem. A company owning a limited fleet of vehicles wants to maximize its operational profit over an infinite horizon divided into periods. The profit stems from revenues for transporting full truckloads and costs derived from waiting idle and moving unladen. The stochastic component of the problem arises from projections on the realization of each transportation order, i.e. load. The methodology is based on optimizing decisions for deterministic scenarios. Several policies are generated in this way, from simple heuristics to more complex approaches, such as consensus and restricted expectation algorithms, up to policies derived from network flow models formulated over subtrees of scenarios. Myopic and a-posteriori deterministic optimizations models are used to compute bounds allowing for performance evaluation. Tests are performed on various instances featuring different number of loads, graph sizes, sparsity, and probability distributions. Performances are compared statistically over paired samples. The robustness of various policies with respect to erroneous évaluations of the probability distributions is also analyzed. [less ▲] Detailed reference viewed: 86 (1 ULg)Multi-period vehicle assignment with stochastic load availability Pironet, Thierry Conference (2014, January 31) We investigate the following problem, which is faced by major forwarding companies active in road transportation (see [2]). A company owning a limited fl eet of vehicles wants to maximize its operational ... [more ▼] We investigate the following problem, which is faced by major forwarding companies active in road transportation (see [2]). A company owning a limited fl eet of vehicles wants to maximize its operational pro fit over an infi nite horizon divided into equal periods (days). The pro fit stems from revenues for transporting full truckloads and from costs derived from waiting idle and moving empty. A decision leading to a set of actions is made at every period and is based on the dispatcher's information over a restricted horizon, called rolling horizon, which subsequently rolls over period per period. The data provided by the customers concern their prospective loads, or requirements for transportation: locations of departure and destination cities, and a unique pick-up period for each load. Moreover, the dispatcher has data regarding travel times between cities, current location and status (empty or loaded) of trucks. These data are known with certainty and represent the deterministic component of the problem. The stochastic component of the problem arises from the uncertainty on the eff ective materialization of each transportation order. More precisely, the availability of each order can be either con rmed, or denied, a few periods ahead of the loading period (meaning that clients con firm their order, which the transporter may still decide to ful ll, or not). For prospective orders in the remote part of the rolling horizon, the dispatcher only knows the order con firmation probability which represents the stochastic load availability. In this setting, trucking orders are provided by the dispatching center to the drivers and to the customers on the eve of the pick-up period at the latest. Typically, the loading decisions are made when all orders are con firmed for the next day. The decision problem faced by the dispatcher is to select or to reject loads, and to assign the selected loads to trucks, taking into account con firmed and expected loads as well as the availability and current location of trucks. The main objective of this research is to provide e fficient algorithmic strategies to tackle this multi-period vehicle-load assignment problem over a rolling horizon including prospective transportation orders. This problem is computationally di fficult owing to the large number of possible realizations of the random variables, and to the combinatorial nature of the decision space. The methodology is based on optimizing decisions for deterministic scenarios. By solving the assignment problem for a sample of scenarios, by mixing solutions and by evaluating them at each period, we aim at finding actions per decision period leading to pro table policies in the long run. Several policies are generated in this way, from simple myopic heuristics to more complex approaches, such as consensus and restricted expectation algorithms [3], up to policies derived from network flow models formulated over subtrees of scenarios. Similar approaches have proved eff ective for other problems; see, e.g., [1]. Myopic and a-posteriori deterministic optimization models are used to compute bounds allowing for performance evaluation. Test are performed on various instances featuring di fferent numbers of loads, graph sizes, sparsity, and probability distributions. Performances are compared statistically over paired samples to assess the signi ficance of the observed differences among algorithmic policies. The robustness of various policies with respect to erroneous evaluations of the probability distributions is also analyzed. Numerical experiments show that the best algorithms close a signi ficant fraction of the gap between the worst (myopic) and best (a posteriori) bounds for a broad range of datasets and for several probability distributions. Furthermore, the subtree algorithm remains quite robust against a variety of probability distributions when it is calibrated with a distribution re flecting maximum uncertainty . Acknowledgements. The project leading to these results was partially funded by the Interuniversity Attraction Poles Programme initiated by the Belgian Science Policy O ffice (grant P7/36). References [1] Arda, Y., Crama, Y., Kronus, D., Pironet, Th., and Van Hentenryck, P. (2013), Multi-period vehicle loading with stochastic release dates, EURO Journal on Transportation and Logistics, pp. 1-27, available on-line http://dx.doi.org/10.1007/s13676-013-0035-z. [2] Powell, W. B. (1996), A stochastic formulation of the dynamic assignment problem, with an application to truckload motor carriers, Transportation Science, Vol. 30, pp. 195-219. [3] Van Hentenryck, P., and Bent,R. W. (2006), Online Stochastic Combinatorial Optimization, MIT Press, Cambridge, Massachussetts. [less ▲] Detailed reference viewed: 28 (5 ULg)Multi-period vehicle assignment with stochastic load availability Pironet, Thierry Conference (2014, February 27) This work investigates optimization techniques for a vehicle-load assignment problem. A company owning a limited fleet of vehicles wants to maximize its operational profit over an infinite horizon divided ... [more ▼] This work investigates optimization techniques for a vehicle-load assignment problem. A company owning a limited fleet of vehicles wants to maximize its operational profit over an infinite horizon divided into periods. The profit stems from revenues for transporting full truckloads and costs derived from waiting idle and moving unladen. The stochastic component of the problem arises from projections on the realization of each transportation order, i.e. load. The methodology is based on optimizing decisions for deterministic scenarios. Several policies are generated in this way, from simple heuristics to more complex approaches, such as consensus and restricted expectation algorithms, up to policies derived from network flow models formulated over subtrees of scenarios. Myopic and a-posteriori deterministic optimizations models are used to compute bounds allowing for performance evaluation. Tests are performed on various instances featuring different number of loads, graph sizes, sparsity, and probability distributions. Performances are compared statistically over paired samples. The robustness of various policies with respect to erroneous evaluations of the probability distributions is also analyzed. [less ▲] Detailed reference viewed: 25 (1 ULg)Multi-period vehicle assignment with stochastic load availability Pironet, Thierry Conference (2014, June 23) This work investigates optimization techniques for a vehicle-load assignment problem. A company owning a limited fleet of vehicles wants to maximize its operational profit over an infinite horizon divided ... [more ▼] This work investigates optimization techniques for a vehicle-load assignment problem. A company owning a limited fleet of vehicles wants to maximize its operational profit over an infinite horizon divided into periods. The profit stems from revenues for transporting full truckloads and costs derived from waiting idle and moving unladen. The stochastic component of the problem arises from projections on the realization of each transportation order, i.e. load. The methodology is based on optimizing decisions for deterministic scenarios. Several policies are generated in this way, from simple heuristics to more complex approaches, such as consensus and restricted expectation algorithms, up to policies derived from network flow models formulated over subtrees of scenarios. Myopic and a-posteriori deterministic optimizations models are used to compute bounds allowing for performance evaluation. Tests are performed on various instances featuring different number of loads, graph sizes, sparsity, and probability distributions. Performances are compared statistically over paired samples. The robustness of various policies with respect to erroneous evaluations of the probability distributions is also analyzed. [less ▲] Detailed reference viewed: 22 (1 ULg)Multi-period vehicle loading with stochastic release dates Arda, Yasemin ; Crama, Yves ; Kronus, David et al in EURO Journal on Transportation and Logistics (2014), 3(2), 93-119 This paper investigates a multi-period vehicle loading problem with stochastic information regarding the release dates of items to be transported. The deterministic version of the problem can be ... [more ▼] This paper investigates a multi-period vehicle loading problem with stochastic information regarding the release dates of items to be transported. The deterministic version of the problem can be formulated as a large-scale set covering problem. Several heuristic algorithms are proposed to generate decision policies for the stochastic optimization model over a long rolling horizon. The resulting policies have been extensively tested on instances which display the main characteristics of the industrial case-study that motivated the research. The tests demonstrate the benefits of the multi-period stochastic model over simple myopic strategies. A simple and efficient heuristic is shown to deliver good policies and to be robust against errors in the estimation of the probability distribution of the release dates. [less ▲] Detailed reference viewed: 206 (53 ULg)Multi-physical processes in geomechanics – an introduction to constitutive modelling and coupling aspects Charlier, Robert ; Dizier, Arnaud ; et al in European Journal of Environmental and Civil Engineering [=EJECE] (2009), 7-8 This paper is the basis for a course dedicated to the geomechanics modelling, taking into account multiphysics couplings. A number of different coupling are discussed, with respectively the fluid flow ... [more ▼] This paper is the basis for a course dedicated to the geomechanics modelling, taking into account multiphysics couplings. A number of different coupling are discussed, with respectively the fluid flow (saturated and unsaturated) and the thermal transfers in deformable porous media. Eventually some aspects on the numerical modelling with the finite element method are discussed. [less ▲] Detailed reference viewed: 101 (20 ULg)Multi-physics modeling Terrapon, Vincent Scientific conference (2010, February) Detailed reference viewed: 16 (4 ULg)Multi-Residue Screening and Confirmatory Analysis of Anabolic Steroids in Urine by Gas Chromatography Coupled with Tandem Mass Spectrometry ; ; De Pauw, Edwin et al in Journal of Chromatography. A (1994), 683(1), 67-74 The diversity of substances used illegally as growth promoters in meat production requires the development of multi-analyte methods of analysis involving a sample pretreatment step that is as rapid and as ... [more ▼] The diversity of substances used illegally as growth promoters in meat production requires the development of multi-analyte methods of analysis involving a sample pretreatment step that is as rapid and as easy as possible, followed by a specific and sensitive determination of several residues within the same run. A general strategy for the screening and confirmatory analysis of fifteen artificial anabolic compounds in urine samples is described. It is based on solid-phase extraction on C18 Empore discs and amino-bonded columns followed, after derivatization (trimethylsilyl or methyloxime-trimethylsilyl derivatives), by gas chromatography coupled with collisionally activated dissociation tandem mass spectrometry. [less ▲] Detailed reference viewed: 50 (2 ULg)Multi-row approaches to cutting plane generation Poirrier, Laurent Doctoral thesis (2012) This thesis focuses on the use of cutting-plane techniques to improve general-purpose mixed-integer linear programming solvers. The first topic covered here is a fast separation method for two-row cuts ... [more ▼] This thesis focuses on the use of cutting-plane techniques to improve general-purpose mixed-integer linear programming solvers. The first topic covered here is a fast separation method for two-row cuts. Two-row cuts are intersection cuts from two rows of a simplex tableau describing the LP relaxation of the problem. This type of cuts recently gathered a lot of attention from the scientific community following a paper by Andersen, Louveaux, Weismantel and Wolsey describing the facets of the underlying two-row model and providing an intuitive geometric classification the the derived cuts. The specificity of the approach adopted here is that it does not rely on an "infinite relaxation" point of view and generate intersection cuts from fixed lattice-free sets. Instead, given a fractional point, it aims at always finding a most violated facet-defining inequality for the two-row model. This can be achieved by optimizing over the polar set of the integer hull of the model. A fast way of performing this is provided, by means of a polyhedron that is equivalent to the polar for that purpose, but has a more compact representation. Moreover, a row-generation algorithm is developed in order to avoid the costly computations of integer hulls of two-dimensional cones. An implementation of the resulting algorithm performs separation of two-row cuts in a few milliseconds on average, on the standard MIPLIB 3 and 2003 testsets. While this two-row separator is quick, the measurements of the computational usefulness of the cuts do not yield satisfactory results. Since all the cuts generated are facet-defining, this might suggest that the underlying two-row models are too weak. This observation prompted the second part of this thesis, an attempt to evaluate the strength of various multi-row relaxations, on small instances, using a generic separator. To that end, a separator is developed, which is able to compute facet-defining inequalities from arbitrary (yet reasonably small) mixed-integer sets. A row-generation approach is again adopted, but this time the slave part consists in the resolution of a mixed-integer problem instead of a closed-form oracle. Some interesting computational tricks are developed, in order to speedup the inherently hard computations. [less ▲] Detailed reference viewed: 98 (28 ULg)Multi-scale analysis of carbon stocks and deforestation monitoring. Case of the Eastern tropical humid forest of Madagascar. ; ; et al in Azevedo, J C; Feliciano, M; Castro, J (Eds.) et al Forest landscapes and Global Change (2010) Detailed reference viewed: 18 (5 ULg)A multi-scale approach to facultative paedomorphosis of European newts (Salamandridae) in the Montenegrin karst: Distribution pattern, environmental variables, and conservation Denoël, Mathieu ; ; et al in Biological Conservation (2009), 142(3), 509-517 Facultative paedomorphosis, a process in which newt larvae can opt for reproduction before or after metamorphosis, is geographically heterogeneous. Despite numerous ecological studies and recent evidence ... [more ▼] Facultative paedomorphosis, a process in which newt larvae can opt for reproduction before or after metamorphosis, is geographically heterogeneous. Despite numerous ecological studies and recent evidence of declines in paedomorphic populations, however, no attempt to model environmental variables that explain the presence of paedomorphs has been made at a multi-scale level. Our aim was to fill this gap in studying three newt species (Lissotriton vulgaris, Mesotriton alpestris, and Triturus macedonicus) of the Montenegrin karst as model species. To this end, we used multivariate analysis on three scales of habitat: the breeding pond, the land use and the climatologic features. Results show that the study area is both an important hotspot for paedomorphosis and where intraspecific diversity is quickly disappearing (20-47% extirpation) because of fish introductions. Other habitat variables (water permanency, PH or the habitat origin) were shown to act on paedomorphosis but not consistently across species, confirming complexity of the evolutionary and ecological processes. This study appeals for more long-term and detailed landscape studies of polyphenisms, a neglected but promising topic, to better understand and protect alternative modes of development. Particularly, measures should be taken to identify hotspots of intraspecific diversity at a global scale and stop fish introductions before we reach a point of no-return. (C) 2008 Elsevier Ltd. All rights reserved. [less ▲] Detailed reference viewed: 378 (30 ULg) |
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